1. Technical Field
Embodiments of this disclosure generally relate to an image forming apparatus such as a copier, a printer, and a facsimile machine, and more specifically, to an image forming apparatus for forming a toner image by developing a latent image on a latent image carrier with a two-component developer and transferring the toner image onto a recording medium.
2. Related Art
In typical electrophotographic image forming apparatuses, optical image data is formed as a latent image on an evenly charged latent image carrier, such as a photoconductor, and the latent image is developed with toner supplied by a developing device to form a visible toner image on the latent image carrier. The visible toner image is then transferred onto a recording medium, such as a transfer sheet, directly or indirectly via an intermediate transfer body, such as an intermediate transfer belt.
In such image forming apparatuses, impaired and insufficiently charged toner may degrade image quality with background contamination or the like. For example, with continuous printing involving few or no images, only a small amount of toner is discharged from the developing device while a large amount of toner remains in the developing device and is circulated for a long time therein. The toner deteriorates with such extended circulation. For example, an additive may be separated from the toner and buried. Such deterioration of toner may increase the viscosity of a developer and/or change charging characteristics of the toner, degrading image quality with background contamination or the like.
One approach to preventing impaired toner from degrading image quality involves forced consumption of the impaired toner contained in the developing device. Such forced consumption of impaired toner contained in the developing device decreases toner density of the developer contained in the developing device and thereby prevents background contamination due to impaired toner. However, excessive decrease in toner density may lower, and therefore degrades image density.
Forced toner consumption is typically performed when an image forming process consumes a small amount of toner contained in the developing device, which impairs the toner in the developing device. When a small amount of toner is consumed, the developing device has a relatively high toner density. Therefore, even after the forced toner consumption, the developing device keeps a sufficient toner density to obtain a desired image density.